Structure and properties of TiBx coatings deposited via magnetron sputtering with ion source etching

Abstract

A common issue in sputter-deposited TiBx is that the films contain excess B. Here we deposited TiBx coatings by dc magnetron sputtering combined with Ar+ ion etching under different currents. The influences of the ion-source current on the structure and mechanical properties of the TiBx coatings were studied using scanning electron microscopy, X-ray photoelectron spectroscopy, nanoindentation, and scratch tests. The tribological performances of the coatings were investigated through ball-on-disk wear tests. The results indicate that the ion source etching could significantly refine the grain structure of the TiBx coating that changes from a typical columnar to smooth glass-like structure as the current of ion source increases. Grain refinement of the TiBx coatings helps to increase the coating hardness and toughness significantly. In addition, the atomic ratio of the Ti over to B in the coatings can be adjusted to optimize the toughness of the TiBx coating. The dc sputter-deposited TiBx was found to be over-stoichiometric (2.10), whereas the Ar+ ion etching preferred to reduce the x and an under-stoichiometric ratio x = 1.95 was obtained when the current was set at 10 A. This makes the coating tough. Therefore, the high toughness suggests that the coating has a high resistance to cracking, exhibiting high adhesion strength. Furthermore, the tool coated with TiBx coating deposition with ion source presented better cutting performance compared with that coated with TiBx coating deposition without ion source.